The present invention relates to a tool, preferably a punch and die set, for use in a shake-and-break process.
A known apparatus used to form shaped parts out of flat metal stock is a turret press, an example of which is disclosed in U.S. Pat. No. 5,685,812. In its simplest form, referring to FIG. 1, a turret press includes an upper rotatable turret 10 and a lower rotatable turret 12, both turrets being in the shape of a disk. The upper rotatable turret 10 includes a number of openings for mounting a plurality of interchangeable punches 14, 14a, two of which are shown for purposes of illustration. The lower rotatable turret 12 includes openings for receiving cooperating dies 16, 16a.
A sheet of metal stock 18 (or alternatively a plurality of nested sheets) is supported horizontally on a table (not shown) which is moveable in any direction in the horizontal plane so as to selectively reposition the sheet 18 relative to the press. A ram 20 is positioned over one of the punches 14 and is mounted on a crankshaft 22 for movement in the vertical direction.
In order to form a shaped part, the turrets 10 and 12 are rotated to move a selected punch and die set 14, 16 under the ram 20. The stock piece 18 is maneuvered so that the material to be removed is located between the punch 14 and die 16, and the ram is actuated to punch a hole in the stock piece 18 corresponding to the shape of the punch face. The sheet 18 is then repositioned for the next punch operation. If a different punch and die set are to be used, i.e., to punch a different shape hole, the turrets 10 and 12 are rotated to position the new punch and die set, e.g., 14a, 16a, below the ram 20. This process is repeated until the part is formed.
In order to save material and labor, several parts are punched in patterns from each sheet of stock material. In a typical operation, a long, rectangular shaped punch is used to cut around the sides of the part, so as to cut it to basic size. However, a plurality of tabs, connecting the several parts formed from the sheet, are left. These tabs hold the parts within the skeleton of the sheet while it is being punched.
After the sheet is removed from the machine, the parts are shaken out of the skeleton, that is, such that the individual parts are separated from the tabs. This tends to leave burrs along the edges of the parts where the opposite ends of the tabs previously were attached, and such burrs need to be removed with an operation known as de-burring. De-burring is time consuming and adds to the cost of producing the parts.